Polyphase x-ray system



Sept. 3, 1935. A. MUTSCHELLER POLYPHASE X-RAY SYSTEM Filed July 1, 1932 2 Sheets-Sheet l I: II: I: I: I I

INVENTOR A Ml/TjCl/EALf/V BY )7 9- /60 in.

A A v A A TlME 0 ATTORNEY /asa Neo '//20 V90 V72 Sept. 3, 1935. A. MUTSCHELLER 2,013,390

7 POLYPHASE X-RAY SYSTEM Filed July 1, 1932 2 Sheets-Sheet 2 INVENTOR A. MVZifl/fLLE/P Patented Sept. 3, 1935 FHQ POLYPHASE X-RAY SYSTEM Arthur Mutscheller, New York,- N. Y., assignor to Westinghouse X-Ray Company, Inc., a corporation of Delaware Application July 1, 1932, Serial No. 620,378

7 Claims.

My invention relates to X-ray systems and par- .ticularlytosuch systems wherein the X-ray tube receives energization by rectified currents from a three phase alternating current source of supply.

In the'prior art three phase sources of energization for an X-ray tube have been utilized with some degree of success. In these systems, however, in order to suitably rectify the energy supplied to the X-ray tube rectifiers must be employed in each phase to obtain full rectification thereof, such for example as vacuum valve tubes. Heretofore this has required a total of six valve tubes or two in each phase.

The radiographic results obtained with these prior art systems require exceptionally critical technique due to the tendency of the X-ray photograph to become flat or lacking in the wide scale of graduation which makes the quality of a successful X-ray photograph. This is peculiar'to the rate at which direct current characteristics are approached in rectified alternating currentiexcitation of an X-ray tube. I have found that by producing a somewhat irregular curve or sign wave of the energy supplied to the X-ray tube, which difi'ers from the usual flat sign waveof three phase rectified energy, radiographs can be produced wherein the definition of theiilm is greatly increased, thus dispensing with the necessity, among other things, for critical technique. v

Moreover, in my novel system I prevent the potential from at .any timedropping .to zero and maintain it at a value which is always radio .graphicallyuseful. By employing onlyfour valve tubes .for rectification purposes I obtain greater emission currentsof the valve tubes and a .bal-

.anced load on each "of the three phases, all of which is a'ldistinct advantage in producing better radiographs over three phasesystems of the prior art.

I-t accordingly an object of my invention to provide an X-ray system wherein a source of three phase rectified energy is utilized to energize an X-ray tube and X -ray photographs are produced with an entire absence of flatness or insufiicient definition of the .film without the .necessityof critical technique.

Another objectof my invention isthe provision of an X-ray system wherein a, sourceof three phase rectified energy is utilized to energize an X-ray tube in whichcomplete rectification thereof is obtained with the "employment of only four rectifying valve tubes.

Another object of my invention is the provision of an X-ray-system wherein a source of three phase rectified energy'is utilized to energize an X-ray tube and in which only four valve tubes are employed for rectification .purposes, with thecontrols for the latterbeing great- 1y simplified byoperationof thesetubesin pairs.

Another object of my invention is the provision of an X-ray system wherein a source of three phase rectified energy is utilized to energize an X-ray tube and in which four valve tubes are employed for rectification purposes, thus lessening the instantaneous emission required for a given amount of X-ray tube current.

A further object of my invention is the provision of an X-ray system wherein a source of three phase rectified energy is utilized to energize an X-ray tube and in which an irregular sign wave of the potential supplied to the X-ray tube is produced with the maximum voltage drop maintained at a useful radiographic value.

Still further objects of my invention will be come apparent to those skilled in the art by reference to the accompanying drawings wherein Figure l is a diagrammatical representation of an X-ray system embodying the features of my invention;

Figure 2 is a diagrammatical representation of the sign wave of the rectified energy of each phase;

Figure 3 is a diagrammatical representation of the resultant sign wave of the superimposed rectified energy supplied to a load;

Figure 4 is a diagrammatical representation of the system shown in Figure 1 indicating the flow of the energy in the system at the start or zero time period;

Figure 5 is a diagrammatical representation of the system shown in Figure 1 indicating the fiow of the energy in the system after the lapse of i th of a second;

Figure 6 is a diagrammatical representation of the system shown in Figure 1 indicating the flow of the energy in the system after the lapse of th of a second;

Figure '7 is a diagrammatical representation of the system shown in; Figure 1 indicating the fiow of the energy in the system after the lapse of th of a second;

Figure 8 is a diagrammatical representation of the system shown in Figure 1 indicating the fiow of the energy in the system after the lapse of 9 6th of a second; and

Figure 9 is a diagrammatical representation of the system shown in Figure 1 indicating the flow of the energy in the system after the lapse of 3nd of a second.

shown a plurality of secondary windings l, 2 and 3. These secondary windings are adapted to be energized by primary windings 4, 5 and 6 respectively. Each of these latter primary windings receive energization from one phase of a three phase source of supply, Ll, L2 and'L3, with these primary windings connected thereto in any suitable manner, such for example as a star connectlon. Although I have shown substantially ,50 Referring now to the drawings in detail I have three separate transformers with the primary windings of each adapted to receive energization from one phase of a polyphase source, it is to be understood that the secondary windings l, 2 and 3 with their respective primaries may constitute a single transformer with the primary and sec ondary windings wound upon a common core.

One end of the secondary winding l is connected to the cathode of two thermionic rectifying valves 1 and 8, by means of conductor 9, which is connected to a common conductor iii, interconnecting the cathodes of these two tubes, In a similar manner the remaining end of this secondary winding is likewise connected to the thermionic cathode of two similar rectifying valve tubes l2 and i3, by means of a conductor M, which is connected to a common conductor l5, interconnecting the cathodes of these two latter tubes.

One end of secondary winding 2 is connected, by means of a conductor l6, to the anode of valve tube 1 and its remaining end is connected, by means of a conductor H, to the anode of valve tube l2. Likewise one end of the secondary Winding 3 is connected, by means of a conductor l8, to the anode of valve tube 8 and its remaining end is connected, by means of a conductor it, to the anode of valve tube iii.

A conductor 22 extends from the mid-point of the secondary winding l to the anode of an X-ray tube 28 (shown in Figures 4 to 9) for supplying uni-directional energy of positive polarity thereto. A conductor 23 extends from the mid-point of the secondary winding 2 to the thermionic cathode of the X-ray tube 2% and is connected to a conductor 24 which extends from the midpoint of the secondary winding 3, in order that negative polarity may be supplied by both of these latter secondary windings to the cathode of the X-ray tube at various periods of time, as hereinafter more fully set forth.

The thermionic cathodes of the valve tubes l and 8 are connected in parallel with a suitable source of low tension heating energy, such for example as batteries or a low tension transformer 25. A variable resistance 26 is connected in series with the cathodes and this source of supply for varying the energy simultaneously applied to the cathodes of both these valve tubes. Regulation of the heating current supplied to the cathodes of these-valve tubes accordingly regulates the energy supplied to the X-ray tube.

Valve tubes I2 and I3 likewise have their respective cathodes connected in parallel with a similar source of low potential energy, such for example as batteries, or a low tension transformer 21', in the same manner as just described relative to the valve tubes I and 8. A variable resistance'or rheostat 28 is likewise connected in series with this latter source and the cathodes of the valve tubes l2 and i3 for regulating the heating temperature of the same and consequently affecting the energy supplied by the respective secondary windings to the X-ray tube.

In Figure 2 I have shown the individual sign wave of the potential of each phase as generated by each respective secondary winding and in Figure 3 the resultant rectified wave supplied to the X-ray tube, which is representative of the aggregate superimposed energy of all phases as supplied to the X-ray tube.

, Although I have constructed a polyphase system in the manner just described and have verified the sign waves of each phase and the resultant sign wave supplied to the X-ray tube, as

shown in Figures 2 and 3, by means of an oscillograph I am unable to explain with any degree of verified certainty the exact electrical phenomenon which takes place within the system. However, my theory of the operation of my system maybe described as follows:

The cathodes of the various valve tubes and the X-ray tube are first energized and regulated to give the desired milliamperes of current by means of the rheostats 2B and 28. A suitable switch (not shown) in the three phase source of supply Ll, L2, L3 is then closed causing the secondary windings I, 2 and 3 to become energized .at different instants of time by their respective primary windings 4, 5 and 6. These primary windings are in turn energized by each phase of the three phase source of supply which at any given instant is supplied by at least two of the respective conductors Ll, L2, L3. This particular phenomena of three phase supply sources being well known in the electrical art I shall refer throughout my specification and claims to the secondary windings l, 2 and 3 of the respective transformers as being directly energized by any one of three phases A, B or C. It must be understood, however, that strictly speaking they are only indirectly energized thereby from the primary windings 4. 5 and 6 by at least two of the supply conductors and no reference is deemed necessary to the particular conductors Ll, L2, L3 supplying any one of these phases at a given moment as they naturally vary with variations in time periods.

Assuming that upon closure of the switch in and C. Although this particular condition is only a momentary one it is necessary to take one phase as a standard in order to make a comparison of the conditions of the remaining phases at a given instant relative to that phase. Secondary winding I which is normally energized by phase A being at the zero point of the wave will,

of comparison. I

Referring now more particularly to Figure 4,

therefore, be taken as standard for the purposes I have shown my theory of the electron flow of the energy in my system at zero time or the start, upon closure of the main line switch. Secondary winding I, as previously stated, is at this instant unenergize d and is accordingly indicated as being at zero potential. by the letter Z.

Secondary winding 2 receives its energy from phase B and we will assume that the upper end of this winding has a positive polarity whereas the lower end has a negative polarity as shown in this figure. Electrons will then flow from the mid-point of secondary winding 72,;through con. ductor 23 to the cathode of the X ray tube 20, through the tube to the anode, back to the 'midpoint of secondary winding l, (which acts at this instant merely as a conductor being un-enerf gized) thence by means of conductors!) and ill, through valve tube 1 and conductor I 6 to'the end of secondary winding 2. This supply of the energy is shown by means of the arrows marked B indicating the energy supplied by phase B.

Secondary winding 3 .at this instant will have a negative polarity impressed upon its upper end and a positive potential upon its lower end which is just the reverse of the polarity just assumed relative to the winding 2. Electrons accordingly will be supplied by conductor 24 to the cathode of the X-ray tube, through the tube and conductor 22 to the mid-point of secondary winding I. The polarity of the upper end of winding 3 being at this instant negative and that of winding 2 positive will not permit the potential supplied by winding 3 and phase 0 to be impressed upon the upper portion of winding I and valve tube 8, but it will be supplied to the lower portion of winding I, then through conductors I4 and I5, valve tube I3, and thence by means of conductor I9, to lower portion of secondary winding 3 as shown by the arrows marked C.

It is to be noted that at this instant the rectified energy supplied by phase B and C passes through the X-ray tube but the potential is not the aggregate of portions of windings 2 and 3, but merelya little more than one-half the sum. This is due to the energy of phase B flowing through the upper portion of secondary winding I while that supplied by the lower portion of winding 3 flows through the lower portion of winding I. This causes va bucking efiect in this latter winding resulting in the X-ray tube being supplied with approximately 60% of the total potential of these two windings, as the energy approaches another time period or, as I have shown, lth of a second.

This is indicated by the drop in the potential supplied to the X-ray tube, as shown in theresultant wave form of Figure 3, as the potential approaches another given period of time.

Figure 5 represents the flow of the energy through the system after a lapse of l/360th of a second. By reference to Figure 2 it will be noted that at this time period phase B has now reached its zero point or" the wave and accordingly secondary winding 2 is now not energized, as shown at Z. Secondary winding l energized by phase A will now assume a positive polarity at its upper end and a negative polarity at its lower end.

. The polarity of secondary winding 3 remains the same as before stated, namely upper end negative and lower end positive, due to the fact thatafter a lapse of only 1/360th of a. second this phase has not as yet reversed but is still in the initial half wave of its respective alternating current cycle.

Electrons, therefore, will flow from the lower portion of winding l through conductors I4 and 95 to valve tube I2, then through conductor I1 and lower portion of winding 2 (now at zero and functioning merely as a conductor), through conductor 23 and the X-ray tube 28, thence back to the mid-point of Winding I by means of conductor 22 as indicated by the arrows showing the flow of energy contributed by phase A. During this same instant electrons flow in the direction of the arrows marked C from winding 3, through conductor 2 the X-ray tube, back to the midpoint of winding 5 by means of conductor 22, then through the lower portion of winding I (in the same direction as phase A), through conductors I l and H5, valve tube It, and thence by means of conductor l9 back to secondary winding 3.

It should be noted that at this particular instant the X-ray tube is supplied with the aggregate potential of windings I and 3 because there is an entire absence of bucking in all the windings thus obviating a drop in the potential resulting in it being maintained at maximum, as shown in Figure 3, after the lapse of 1/360th of a second.

It should also be here stated that the X-ray tube is not supplied with 100% of the potential of windings l and 3. This can doubtlessly be appreciated by reference to Figure 2 wherein it can be readily seen that the potential of phase A is approaching its peak whereas that of phase 0 is receding. Accordingly when one phase reaches its peak the one closest thereto is either approaching its respective peak, or receding therefrom. This results, for example, in the X- ray tube being energized, at the peak of any one phase, with 160% of the potential of that particular phase and approximately 90% of the total potential of the nearest phase thereto, or approximately 95% of the aggregate potential of these two phases with the remaining phase assumed to be at the zero point of the wave. This same analogy holds true at the start or zero time period previously described where, due to the aforementioned bucking effect, the potential does not drop to one half the total or" two phases, but to only approximately 60% of the total.

Passing now to the lapse of 1/ 180th of a second it will be noted in Figure 2 that phase C has reached its zero point of the wave, as indicated at Z. Secondary winding 3, as shown in Figure 6 is now Lin-energized. Both secondary windings i and 2 are now, however, energized. The polarity of secondary winding 5 remains as previously described relative to Figure 5, namely, upper end positive and lower end negative, as it has not completed its half wave.

Secondary winding 2, which at 1/360th of a second was un-energized by phase B, is now impressed with a positive potential at its lower end and a negative potential at its upper end. This polarity, it should be noted, is just the reverse of that described relative to Figure 4 as this particular phase (B) has now passed through one half wave of its respective cycle.

Electrons will now flow from the mid-point of winding 2, as noted by the arrows marked B, in the following manner: through conductor 23 to the X-ray tube Zil, through conductor 22 to the mid-point of secondary winding I, then through the lower portion of winding I, conductors I4 and I5, valve tube I2 and thence to the lower portion of secondary winding 2 by means of conductor Il. Likewise secondary winding I supplies electrons, as shown by the arrows A, from its negative end, through conductors Id and I5, valve tube I3, conductor I9 to the lower portion of secondary winding 3. This winding having zero potential acts merely as a conductor and the electron flow passes to the X-ray tube 29 through conductor 2 and thence back to the mid-point of secondary winding I. In a similar manner, as just mentioned relative to Figure 5, the electron fiow through the lower portion of winding l of both phases A and B is in the same direction thus obviating any bucking efiect. This again maintains the potential at its maximum as shown in Figure 3 after a lapse of 1/ 180th of a second.

Referring now to Figure '7 I have indicated the flow of electrons in my system after the lapse of l/120th of a second. At this particular instant phase A has again reached its zero point of the Wave and accordingly secondary winding I is un-energized, which is shown by the letter Z.

Secondary winding 3, which previously was at zero potential at l/l80th of a second, new receives energy from phase C. A positive polarity will therefore be impressed upon the upper end of this secondary winding and a negative potential upon the lower end. The polarity of secondary winding 2 remains the same as that after the lapse of 1/ 180th of a second, namely, lower end positive, upper end negative, it being still in the same half wave of its cycle. Electrons again flow in the direction indicated by the arrows marked B, namely, through conductor 23, X-ray tube 28, then to the mid-point of secondary winding I, through a lower portion of this winding (which now is at zero and functions merely as a conductor), through conductors I I and I5, valve tube I2, thence by means of conductor II to the lower end of secondary winding 2.

In the same instant secondary winding 3 likewise supplies electron fiow to the X-ray tube in the direction indicated by the arrows marked C, as follows: through conductor 2&- and X-ray tube 2|], then through conductor 22 to the mid-point of secondary winding I. The polarity of the lower end of secondary winding 3 being now negative and the lower end of secondary winding 2 being positive, the electrons contributed by phase C accordingly will not flow through valve tube I3, but will flow through the upper portion of secondary winding I, through conductors 9 and Ill, valve tube 8, back to the upper end of secondary winding 3, through conductor I8.

Again it will be noted that the flow of the energy contributed by phase B is through the lower portion of secondary winding I, whereas that contributed by phase C is through the upper portion of secondary winding I. A bucking efiect is again existent analogous to that previously described relative to Figure 4. However, there is still this differentiation therefrom in that in Figure 4 energy contributed by phase B flows through the upper portion of secondary winding I and that of phase C flows through the lower portion of secondary winding I, whereas at this instant of time, namely 1/ 120th of a second the direction of the flow of energyof these respective phases have now reversed their direction of flow. This bucking effect caused by opposite flow of energy of the two phases through secondary winding I again causes a drop in the voltage, as shown in Figure 3, after the lapse of 1/ 120th of a second in the same manner as at the start or zero time period.

Passing now to another time period or after the lapse of 1/ 90th of a second, Figure 8 is illustrative of the electron flow in the system after the lapse of this period of time. It will be noted by reference to Figure 2 that phase B has now reached its zero point of the wave and accordingly secondary winding 2 is unenergized. This is shown by secondary winding 2 at Z or no potential. Secondary winding I on the other hand, which at 1/12Ilth of a second was at zero, now becomes energized by phase A and its upper end will assume a negative potential, whereas its lower end is impressed with a positive potential. It should be noted that this is the reverse condition of secondary winding I and phase A described relative to Figure 5, as phase A has now passed its zero point of the wave and is in the second half wave of its respective alternating current cycle which accordingly reverses the direction of the flow of energy.

Secondary winding 3 has the same polarity impressed upon its'respective ends as that referred to relative to Figure 7, or namely, upper end positive and lower endv negative, due to the fact that phase C is still in the same direction'of flow.

Electrons will accordingly flow from the upper end of secondary winding I to the X-ray tube,

in the direction as indicated by the arrows marked A, in the following manner: through conductors 9 and IE3, valve tube I, conductor I6, through the upper portion of secondary winding 2 (which is now at zero and functions merely as a conductor) then from the mid-point of this winding through conductor 23 to the X-ray tube 20 and thence back to the mid-point of secondary winding I, through conductor 22.

During this same instant electrons will flow from the midpoint of secondary winding 3 through conductor 24, X-ray tube 20 and back to the midpoint of secondary winding I by means of conductor 22, then through the upper portion of secondary winding I in the same manner as just stated relative. to the flow of energy of phase A, then through conductors 9 and It, valve tube 8, back to the upper end of the secondary winding 3 by means of conductor I8, as indicated by the arrows marked C.

It thus becomes apparent that the X-ray tube is again energized by the aggregate potential of the upper portion of the secondary windings I and 3. The X-ray tube is, therefore, again energized by substantially the aggregate potential of each portion of these respective windings and the maximum potential is again maintained, as

obvious from the resultant sign wave at 1/90th' its wave and accordingly secondary winding 3 is not energized thereby, as indicated by Z in this.

figure. Also phase B, which at 1/90th of a second was at zero potential and accordingly did not energize secondary winding 2, now supplies a positive potential to the upper end of secondary winding 2 and a negative potential to the lower 7 end thereof. 7

This polarity is now the reverse of that described relative tothis winding in Figure 6 as phase B,'which energizes this winding, is now in the second half wave of its respective alter,- nating current cycle. Secondary winding I, which is energized by phase A, maintains the same polarity just described relative to the lapse of l/90th of a second, namely, lower end positive and upper end negative. Electrons now flow from the mid-point of secondary winding '2 in the direction indicated by the arrows B, through conductor 23 to the X-ray tube, through the X- ray tube ZII and conductor 22'to the mid-point of secondary winding I, thence through the upper portion of this winding, through conductors e and I I] and valve tube I, back to the upper end of secondary winding 2, by means of conductor I 6.

At the same instant electrons flow from the upper end of secondary winding 1, through conductors 9 and Ill, valve tube 8, to the upper end of secondary winding 3, through conductor I8, thence through this winding (which is now at ,zero and accordingly'functions, merely as a conwinding l by means of conductor 22, in the manner as indicated by the arrows marked A.

Again at this particular instant of time the X-ray tube is supplied with the aggregate potential now contributed by the upper portions of secondary windings I and 2, which maintains the total potential supplied to the X-ray tube at its maximum as shown in the resultant sign wave of Figure 2, at 1/72nd of a second.

The next time period appearing under the abscissa of Figure 2 is that after the lapse of 1/60th of a second, which is obviously one complete cycle of the alternating current. The condition within the circuit is therefore identical with that previously described with reference to Figure 4, which was the start or zero time period.

Having described the flow of energy through my system at various periods of time for one complete cycle the operation is therefore identical for all remaining cycles during the period of energization of the X-ray tube by closure of the main time switch (not shown) in the source of polyphase energy A, B and C.

It, therefore, can be readily appreciated by those skilled in the art that in my novel polyphase system each one of the phases is equally prominent in the energization of the X-ray tube even for the short periods when a bucking effect exists within the system. Upon the occurrence of this bucking condition the voltage drop reaches a minimum of only approximately 60% of the maximum potential supplied to the tube, which is nevertheless still radiographically useful. The load impressed on each phase is also substantially equal throughout the entire period of energization of the X-ray tube. Moreover, all three phases deliver energy of the proper polarity to the secondary or X-ray tube circuits, due to the complete rectification of each phase by the utilization of only four rectifying valve tubes.

Due to the notches of potential drop in the resultant wave form of the superimposed phases, as supplied to the X-ray tube, a substantial amount of soft X-rays emanate from the X-ray tube. This tends to obviate flatness and give good definition, of the soft body parts upon the resulting radiographic film, whereas the full voltage causes the emanation of the higher penetrative X-rays which outline the bones and thicker portions of the body. This all contributes to the successful pictures obtainable with my system.

It should also be noted that each rectifying valve tube conducts impulses from two phases, but at different instances of time, hence less instantaneous emission is required for these valve tubes for a given amount of X-ray tube current which leads to longer life of the valve tubes than with polyphase systems of the prior art.

In providing a unitary source of heating current for the cathodes of the vacuum tubes and a control therefore, the control of the entire system is considerably simplified. Although I have shown the control of the valve tubes in pairs it is to be understood that all four of these tubes may be energized from a single source and controllable by a single rheostat with equally successful results.

Furthermore, in showing and describing a polyphase system utilizing only three phases it is to be understood that the same features are equally applicable to other polyphase systems wherein more than three phases are utilized. Such for example, as a four phase system wherein four secondary windings are employed each being energized by one phase from the source with the mid-point of two of these windings supplying the positive polarity to the X-ray tube and the mid-point of the remaining two secondary windings supplying the negative potential thereof.

In showing this specific embodiment of my in vention I do not desire to be limited thereto as various other modifications of the same may be made without departing from the spirit and scope of the appended claims.

What is claimed is:

1. In an X-ray system, the combination with an X-ray tube having electrodes therein, of a plurality of secondary windings for supplying energy to said X-ray tube, a polyphase sourceof electrical energy each phase of which is adapted to energize a separate one of said secondary windings, a vacuum valve tube connected to each end of all of said secondary windings for rectifying the energy supplied by said windings to said X-ray tube, and connections from the mid-points of two of said secondary windings to one electrode of said X-ray tube and from the midpoint of the remaining secondary winding to the other electrode of said X-ray tube.

2. In an X-ray system, the combination withan X-ray tube having an anode and a cathode, of a plurality of secondary windings for supplying energy to said X-ray tube, a polyphase source of electrical energy each phase of which is adapted to energize a separate one of said secondary windings, a pair of vacuum valve tubes having their cathode terminals connected to one end of one of said secondary windings and their respective anode terminals connected to one end of each of said remaining secondary windings, a second pair of vacuum valve tubes having their cathode terminals connected to the remaining end of the same secondary winding as said first mentioned pair of valve tubes and their respective anode terminals connected to the remaining end of each of said remaining secondary windings, said pairs of vacuum valve tubes being operative to rectify the energy supplied by all of said secondary windings to said X-raytube, and connections from the mid-point of said secondary winding, having the cathodes of said valve tubes connected thereto, to the anode of said X-ray tube, and from the mid-points of said remaining secondary windings to the cathode of said X-ray tube.

3. In an X-ray system, the combination with an X-ray tube provided with electrodes energized by rectified alternating current from a polyphase source of supply, of a plurality of secondary windings for supplying energy to said X-ray tube, a polyphase source of electrical energy each phase of which is adapted to energize a separate one of said secondary windings, a pair of thermionic vacuum valve tubes having their cathode terminals connected to one end of one of said secondary windings and their respective anode terminals connected to one end of each of said remaining secondary windings, a second pair of vacuum valve tubes having their cathode terminals connected to the remaining end of the same secondary winding as said first mentioned pair of valve tubes and their respective anode terminals connected to the remaining end of each of said remaining secondary windings, said pairs of valve tubes being operative to rectify the energy supplied by all of said secondary windings to said X-ray tube, a source of energy for heating the cathodes of each pair of valve tubes provided with regulating means for controlling the emissivity of each pair, connections from the mid-point of one of said secondary windings to one electrode of said X-ray tube and from the mid-points of the remaining secondary windings to the other electrode of said X-ray tube.

4. In an Y-ray system, the combination with an X-ray tube provided with electrodes energized by rectified alternating current from a polyphase source of supply, of a plurality of secondary windings for supplying energy to said X-ray tube, a

polyphase source of electrical energy, each phase of which is adapted to energize a separate one of said secondary windings, a vacuum valve tube connected to each end of all said secondary windings for rectifying the energy supplied by at least two said secondary windings at different periods of time upon energization of the latter by its respective phase, and connections from the midpoint of one of said secondary windings to one electrode of said X-ray tube and from the midpoints of the remaim'ng secondary windings to the other electrode of said X-ray tube for supplying the latter with unidirectional energy during each half wave of the alternating current cycle of each phase.

5. In an X-ray system, the combination with an X-ray tube provided with electrodes energized by rectified alternating current from a polyphase source of supply, of a plurality of secondary windings for supplying energy to said'X-ray tube, a polyphase source of electrical energy each phase of which is adapted to energize a separate one of said secondary windings, a vacuum valve tube connected to each end of all said secondary windings for rectifying the energy supplied by each of said windings and for superimposing the energy of each individual secondary winding upon that of the remaining secondary windings as the latter are energized by their respective phase from said polyphase source, and connections from the midpoint of one of said secondary windings to one electrode of said X-ray tube and from the mid-points of the remaining secondary windings to the other electrode of said X-ray tube for supplying the latter with the superimposed rectified energy of each secondary winding during each half wave of the alternating current cycle of each phase.

6. In an X-ray system the combination with an X-ray tube energized by rectified alternating current energy from a po-lyphase source of supply of a plurality of secondary windings for supplying energy to said X-ray tube, a polyphase source of electrical energy, each phase of which is adapted to energize a separate one of said secondary windings, vacuum valve tubes connecting one end of all of said secondary windings together and connecting the opposite end of all of said windings together to form a circuit including all of said entire secondary windings in electrical parallel relationship with respect to each other for rectifying each half Wave of the alternating current cycle supplied by each phase to the respective secondary winding, and connections from the midpoint of each secondary winding to said X-ray tube for supplying the latter with uni-directional energy from said windings. '7. In an X-ray system the combination of an X-ray tube energized by rectified alternating current energy from a polyphase source of supply, of a plurality of secondary windings, a polyphase source of electrical energy each phase of which is adapted to energize a separate one of said secondary windings, vacuum valve tubes connecting one end of all of said secondary windings together, and connecting the opposite end of all of said windings together to form a circuit, including all of said entire secondary windings in electrical parallel relationship with respect to each other for rectifying the energy supplied by said windings, connections from the midpoint of each of said secondary windings to said X-ray tube, a circuit for energizing said X-ray tube during one half wave of the alternating current cycle including a portion of each of said secondary windings, two of said valve tubes and said connections, and a circuit for energizing said X-ray tube during the remaining half wave of the alternating current cycle, including the remaining portion of each of said secondary windings, the remaining valve tubes and said connections.

ARTHUR MUTSCHELLER. 

